Piston pump for a high-pressure cleaning appliance

ABSTRACT

A piston pump for a high-pressure cleaning appliance is provided, including a plurality of pump chambers, into each of which one piston which is movable back and forth plunges, and which are each in flow connection via a suction valve with a suction inlet and via a pressure valve with a pressure outlet, the suction valve including a suction valve closing member which is sealingly positionable on a suction valve seat, and the pressure valve including a pressure valve closing member which is sealingly positionable on a pressure valve seat, the pressure valve seat and the suction valve seat being at different radial distances from a longitudinal pump axis. To increase piston pump mechanical stability without increasing material thickness, the pressure valve seat can be arranged, in relation to the longitudinal pump axis, offset from the suction valve seat in the circumferential direction of the piston pump.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of international application number PCT/EP2012/050869, filed on Jan. 20, 2012, which is incorporated herein by reference in its entirety and for all purposes.

BACKGROUND OF THE INVENTION

The invention relates to a piston pump for a high-pressure cleaning appliance, comprising a plurality of pump chambers, into each of which one piston which is movable back and forth plunges, and which are each in flow connection via a suction valve with a suction inlet and via a pressure valve with a pressure outlet, the suction valve comprising a suction valve closing member which is sealingly positionable on a suction valve seat, and the pressure valve comprising a pressure valve closing member which is sealingly positionable on a pressure valve seat, the pressure valve seat being arranged, in relation to a longitudinal pump axis, radially offset from the suction valve seat.

Such a piston pump is known from WO 2008/086950 A1. By means of it, a liquid, in particular, water, can be pressurized and, for example, directed at a surface or an article in order to clean the surface or the article. The piston pump comprises a plurality of piston chambers into each of which one piston plunges. The piston is reciprocatingly driven. This has the consequence that the volume of the pump chamber changes periodically and, as a result, liquid can be drawn from a suction inlet via a suction valve into the pump chamber, pressurized in the pump chamber and then discharged via a pressure valve and a pressure outlet. A supply line, for example, can be connected to the suction inlet, and a pressure hose, for example, carrying at its free end a discharge member, for example, a spray nozzle or a spray lance, can be connected to the pressure outlet.

While in operation, the piston pump is subjected to considerable mechanical stress as it must withstand liquid pressures of more than 100 bar. Therefore, the housing of the piston pump usually has a substantial material thickness. This applies, in particular, to the area between the suction valve seats and the pressure valve seats as the pump housing is particularly highly stressed in these areas.

The object of the present invention is to develop a piston pump of the kind mentioned at the outset in such a way that it has an increased mechanical stability without increasing its material thickness.

SUMMARY OF THE INVENTION

This object is accomplished, in accordance with the invention, in a piston pump of the generic kind in that the pressure valve seat is arranged, in relation to the longitudinal pump axis, offset from the suction valve seat in the circumferential direction of the piston pump.

Associated with each pump chamber of the piston pump are a suction valve seat and a pressure valve seat. The center points of the suction valve seat and the pressure valve seat are usually positioned in a common section plane of the piston pump, with the section plane containing the longitudinal pump axis. In renunciation of such an arrangement, the pressure valve seat in the piston pump in accordance with the invention is arranged, in relation to the longitudinal pump axis, offset from the suction valve seat in the circumferential direction of the piston pump. It has been found that an increased mechanical stability is imparted to the piston pump by the offset arrangement of the pressure valve seat without the material thickness of the piston pump having to be increased for this purpose. Therefore, the liquid to be pumped can be put under a higher pressure with the material thickness remaining the same.

It is expedient for the pressure valve seat to be arranged, in relation to the longitudinal pump axis, offset at an angle of 10° to 40° from the suction valve seat. In particular, an angle in the range of between 20° and 30°, for example, 25°, has proven advantageous for increasing the mechanical stability of the piston pump without increasing its material thickness.

In relation to the longitudinal pump axis, the pressure valve seat is expediently arranged at the same level as the suction valve seat in the axial direction.

The suction valve seat and the pressure valve seat are advantageously made of a plastic material.

In an advantageous embodiment, the piston pump comprises three suction valve seats arranged so as to be uniformly distributed about the longitudinal pump axis and three pressure valve seats arranged so as to be uniformly distributed about the longitudinal pump axis. In such a configuration, the suction valve seats are arranged at an angular distance of 120° from one another, and the pressure valve seats are also at an angular distance of 120° from one another. Both the suction valve seats and the pressure valve seats, therefore, form the corner points of an imaginary equilateral triangle. Here the center point of the imaginary triangle of the suction valve seats coincides with the center point of the imaginary triangle of the pressure valve seats. However, the imaginary triangle of the pressure valve seats is arranged so as to be rotated about the longitudinal piston axis in relation to the imaginary triangle of the suction valve seats. The angle of rotation is expediently 10° to 40°, in particular, 20° to 30°, preferably 25°.

In a particularly preferred configuration, the piston pump in accordance with the invention comprises a pump block and a pump head, the pump head comprising the suction inlet and the pressure outlet, and the pump block comprising the pump chambers and accommodating the suction valves and the pressure valves, and the pump head being fitted on a triangular rim of the pump block, the suction valves, in a plan view of the pump block, being arranged in the corner areas of the rim, and the pressure valves, in a plan view of the pump block, being surrounded by a cylindrical inside wall within the rim. Such a configuration imparts a particularly high mechanical stability to the piston pump without the material thickness of the piston pump having to be substantially increased for this purpose.

The suction valves each comprise a suction valve passage which is closable by the suction valve closing member, and a suction valve closing spring which acts upon the suction valve closing member with a spring force in the direction of the suction valve passage. Here it is advantageous for the suction valve closing spring to be positioned at an axial distance from the suction valve passage. In such a configuration, the liquid flowing into the pump chamber can flow past the sides of the suction valve closing spring without it necessarily having the liquid flow through it. This reduces flow losses in the area of the suction valve closing spring as the flow loss exerted by the suction valve closing spring can be kept low.

The suction valve closing spring is preferably arranged in a suction valve chamber which is in flow connection with a pump chamber via the suction valve passage, a retaining arm, on which the suction valve closing spring is supported, projecting into the suction valve chamber at a distance from the suction valve passage. In known piston pumps, the suction valve closing spring is directly supported on the suction valve passage, and the liquid has to flow through the suction valve closing spring in order to get to the suction valve passage. In a further development of the invention this is not necessary as the suction valve closing spring is supported with its end that faces the suction valve passage on a retaining arm which projects into the suction valve chamber at a distance from the suction valve passage.

Expediently, the retaining arm is radially aligned in relation to the longitudinal piston axis.

In an advantageous embodiment of the invention, the retaining arm only penetrates the suction valve chamber partially, i.e., the retaining arm stands away from the wall of the suction valve chamber without reaching the diametrically opposed wall area of the suction valve chamber with its free end.

It may, for example, be provided that the retaining arm only projects to about the middle of the suction valve chamber.

It is expedient for the retaining arm to form a guide for the suction valve closing member. It is thereby possible in a constructionally simple way to prevent the suction valve closing member from tilting during a lifting movement.

The retaining arm expediently comprises a through-opening through which the suction valve closing member passes.

The suction valve closing member may, for example, be of mushroom-shaped configuration and comprise a valve disk having a valve shaft connected thereto, the valve shaft passing through the through-opening of the retaining arm and being guided by the retaining arm.

It is particularly expedient for the suction valve closing spring to be clamped on the side of the retaining arm that faces away from the suction valve passage between the retaining arm and the suction valve closing member. In such a construction, the suction valve closing spring is supported, on the one hand, on the side of the retaining arm that faces away from the suction valve passage and, on the other hand, on the suction valve closing member. The suction valve closing member may have a spring holder for this purpose. The spring holder is expediently press-fitted to a shaft of the suction valve closing member.

The following description of a preferred embodiment of the invention serves for further explanation in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic longitudinal sectional view of an advantageous embodiment of a piston pump in accordance with the invention;

FIG. 2 shows a plan view of a pump block of the piston pump from FIG. 1;

FIG. 3 shows a sectional view of the pump block along line 3-3 in FIG. 2;

FIG. 4 shows a sectional view of a suction valve along line 4-4 in FIG. 3; and

FIG. 5 shows a sectional view of the pump block along line 5-5 in FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

An advantageous embodiment of a piston pump in accordance with the invention, generally denoted by reference numeral 10, is shown schematically in the drawings. It comprises a pump head 12 with a suction inlet 14 and a pressure outlet 16. A supply line, via which liquid to be pressurized can be supplied to the piston pump 10, can be connected to the suction inlet 14. A discharge line, via which the liquid pressurized by the piston pump 10 can be directed at an article or a surface in order to clean the article or the surface, can be connected to the pressure outlet 16. The discharge line can carry at its free end a discharge member, for example, a spray lance or a spray nozzle.

The pump head is fitted on a pump block which comprises a total of three identically constructed pump chambers, into each of which one piston plunges. FIGS. 1, 3, 4, and 5 show one of the piston chambers 20 into which a piston 22 extends. A suction valve 24 and a pressure valve 26 are associated with each pump chamber 20. Via the suction valve 24 liquid can be drawn from the suction inlet 14 into the pump chamber 20, and via the pressure valve 26 the liquid pressurized in the pump chamber 20 can escape from the pump chamber 20.

The suction valves 24 each comprise a suction valve closing member 28 which is sealingly positionable on a suction valve seat 30. The suction valve seat 30 surrounds a suction valve passage 32. Via the suction valve passage 32, the pump chamber 20 is in flow connection with a suction valve chamber 34 formed in the pump block 18 on the side of the pump block 18 that faces the pump head 12. Projecting into the suction valve chamber 34 at an axial distance from the suction valve passage 32 is a retaining arm 36, which extends to about the middle of the suction valve chamber 34 and has a through-opening 38 in alignment with the suction valve passage 32.

The suction valve closing member 28 is of mushroom-shaped configuration. It comprises a valve disc 40 which projects into the pump chamber 20 and is integrally adjoined by a valve shaft 42 which passes through the suction valve passage 32 and extends into the suction valve chamber 34. The valve shaft 42 passes through the through-opening 38 of the retaining arm 36 and carries at its free end a spring holder 44 which is pressed onto the valve shaft 42. A suction valve closing spring 46 is clamped between the spring holder 44 and the retaining arm 36. The suction valve closing spring 46 is configured as a helical spring and surrounds the valve shaft 42 in the area between the retaining arm 36 and the spring holder 44. The valve disc 40 of the suction valve closing member 28 is pressed against the suction valve seat 30 under the action of the suction valve closing spring 46.

The pressure valve 26 has a pressure valve closing member 48 which is pressed by a pressure valve closing spring 50 against a pressure valve seat 52. The pressure valve 26 is arranged in a pressure valve chamber 54.

A suction valve chamber 34 and a pressure valve chamber 54 are associated with each pump chamber 20 of the piston pump 10, and all of the pressure valve chambers 54 of the piston pump 10 merge into a common central chamber 56 which is formed by the pump block 18 and the pump head 12. Inserted in the central chamber 56 is a central insert part 58 which is surrounded by sealing rings and has a central passage 60 which is closable by a central closing member 62. The closing member 62 forms in combination with the central insert part a central check valve to which a pressure line 66, aligned coaxially with a longitudinal pump axis 64, is connected, via which the central chamber 56 is in flow connection with the pressure outlet 16.

The pump head 12 is fitted in the axial direction on the pump block 18 with the interposition of an elastically deformable element. In the illustrated embodiment, the elastically deformable element is configured as a sealing ring 68. The sealing ring 68 surrounds a collar-shaped rim 70 of the pump block 18. This is evident, in particular, from FIG. 2. The rim 70 has the shape of an equilateral triangle with rounded corner areas. With reference to a plan view of the pump block 18, the suction valves 24 are each arranged in a corner area of the rim 70. This is evident, in particular, from FIG. 2. The rim 70 surrounds a cylindrical inside wall 72 which in the area of the pump block 18 defines the central chamber 56. In a plan view of the pump block 18, the pressure valves 26 are arranged within the inside wall 72. This is also evident from FIG. 2.

As mentioned above, a suction valve 24 with a suction valve seat 30 and a pressure valve 26 with a pressure valve seat 52 are associated with each pump chamber 20. As is evident, in particular, from FIG. 2, the respective pressure valve seat 52 is arranged, in relation to the longitudinal pump axis 64, offset from the suction valve seat 30 in both the radial direction and the circumferential direction of the piston pump 10. The radial distance of the pressure valve seat 52 from the longitudinal pump axis 64 is less than the radial distance which the suction valve seat 30 assumes from the longitudinal pump axis 64, and in the circumferential direction of the piston pump 10, the pressure valve seat in the illustrated embodiment is offset through an angle α of about 25° from the suction valve seat 30.

The piston pump 10 has a total of three suction valve seats 30 and three pressure valve seats 52, with the suction valve seats 30 as well as the pressure valve seats 52 defining an imaginary equilateral triangle. The center points of the imaginary triangles are arranged on the longitudinal pump axis 64, but the imaginary triangle of the pressure valve seats 52 is rotated about the longitudinal pump axis 64 through the angle α of 25° to the imaginary triangle of the suction valve seats 30.

Adjoining the pump block 18 in the axial direction, in relation to the longitudinal pump axis 64, is a support shield 74 made of a plastic material with three cylindrical support sleeves 78, each in alignment with a longitudinal piston axis 76. The support sleeves 78 are each welded to an annular wall 80 of the pump block 18, which extends into the respective support sleeve 78 and surrounds a sealing ring 82 which lies by way of a sealing lip sealingly against the piston 22.

The support shield 74 is supported in the axial direction on a guide shield 84. The guide shield 84 has three cylindrical guide sleeves. One guide sleeve 86 is recognizable in FIG. 1. The guide sleeves 86 form guide elements for the pistons 22 and are aligned coaxially with the respective longitudinal piston axis 76. The guide shield 84 forms a cover of convex construction, which is seated on a swash plate housing 88 in which a swash plate 90 is mounted for rotation about the longitudinal pump axis 64. Each piston 22 is pressed by a resetting spring 92 against the swash plate 90. This makes it possible by way of a rotational movement of the swash plate 90 to move the pistons 22 back and forth in the axial direction in relation to the longitudinal pump axis 64, so that the volumes of the pump chambers 20 are periodically changed. The swash plate 90 is driven in the usual way by means of a drive motor, known per se and, therefore, not shown in the drawings, for example, an electric motor, which is coupled by way of a gearing 94, shown only schematically in FIG. 1, with the swash plate 90.

When the piston 22 moves backwards in the direction facing away from the pump head 12, liquid is drawn in from the suction inlet 14 via the suction valve chamber 34 and the suction valve passage 32 into the pump chamber 20, and the suction valve closing member 28 lifts off from the suction valve seat 30 counter to the action of the suction valve closing spring 46 and opens the suction valve passage 32. The liquid can thereby flow within the suction valve chamber 34 past the sides of the suction valve closing spring 46 and, therefore, is only subject to low flow losses in the suction valve chamber 34.

When the piston 22 then moves forwards in the direction facing the pump head 12, the suction valve closing member 28 transfers to the its closed position in which it lies sealingly against the suction valve seat 30, as shown in FIGS. 3, 4 and 5. The liquid is thereupon pressurized in the pump chamber 20 until the pressure valve closing member 48 lifts off from the pressure valve seat 52 counter to the closing force of the pressure valve closing spring 50 and thus opens the flow connection between the pump chamber 20 and the central chamber 56. The pressure valve closing spring 50 is supported on the central insert part 58, the passage 60 of which is opened by the central closing member 62 so that the pressurized liquid can flow via the pressure line 66 to the pressure outlet 16.

The liquid can be pressurized in the pump chamber 20 to a pressure of more than 100 bar. In spite of a relatively low material thickness, the pump block 18 made of a plastic material can withstand the high pressures of the liquid. To this end, the pressure valve seats 52 are arranged, as already explained above, offset from the suction valve seats 30 in the radial direction and in the circumferential direction in relation to the longitudinal pump axis 64. The piston pump 10 is, therefore, distinguished by high mechanical stability and relatively low material thickness. 

1. A piston pump for a high-pressure cleaning appliance, comprising a plurality of pump chambers, into each of which one piston which is movable back and forth plunges, and which are each in flow connection via a suction valve with a suction inlet and via a pressure valve with a pressure outlet, the suction valve comprising a suction valve closing member which is sealingly positionable on a suction valve seat, and the pressure valve comprising a pressure valve closing member which is sealingly positionable on a pressure valve seat, the pressure valve seat and the suction valve seat being at different radial distances from a longitudinal pump axis, and the pressure valve seat being arranged, in relation to the longitudinal pump axis, offset from the suction valve seat in the circumferential direction of the piston pump.
 2. The piston pump in accordance with claim 1, wherein the pressure valve seat is arranged, in relation to the longitudinal pump axis, offset at an angle of 10° to 40° from the suction valve seat.
 3. The piston pump in accordance with claim 1, wherein the pressure valve seat is arranged, in relation to the longitudinal pump axis, at the same level as the suction valve seat in the axial direction.
 4. The piston pump in accordance with claim 1, wherein the piston pump comprises three suction valve seats arranged so as to be uniformly distributed about the longitudinal pump axis and three pressure valve seats arranged so as to be uniformly distributed about the longitudinal pump axis.
 5. The piston pump in accordance with claim 1, wherein the piston pump comprises a pump block and a pump head, the pump head comprising the suction inlet and the pressure outlet, and the pump block comprising the pump chambers and accommodating the suction valves and the pressure valves, and the pump head being fitted on a triangular rim of the pump block, the suction valves, in a plan view of the pump block, being arranged in the corner areas of the rim, and the pressure valves, in a plan view of the pump block, being surrounded by a cylindrical inside wall within the rim.
 6. The piston pump in accordance with claim 1, wherein the suction valves each comprise a suction valve passage which is closable by the suction valve closing member, and a suction valve closing spring which acts upon the suction valve closing member with a spring force in the direction of the suction valve passage, the suction valve closing spring being positioned at an axial distance from the suction valve passage.
 7. The piston pump in accordance with claim 6, wherein the suction valve closing spring is arranged in a suction valve chamber which is in flow connection with a pump chamber via the suction valve passage, a retaining arm, on which the suction valve closing spring is supported, projecting into the suction valve chamber at an axial distance from the suction valve passage.
 8. The piston pump in accordance with claim 7, wherein the retaining arm forms a guide for the suction valve closing member.
 9. The piston pump in accordance with claim 7, wherein the retaining arm comprises a through-opening through which the suction valve closing member passes.
 10. The piston pump in accordance with claim 9, wherein the suction valve closing spring is clamped on the side of the retaining arm that faces away from the suction valve passage between the retaining arm and the suction valve closing member. 